The present invention relates to hardware for the launch, transportation, transfer, and release of satellites, cargo, and other payloads in earth orbit. More particularly, the present invention relates to a satellite dispenser providing propulsion and avionics systems for the controlled release of multiple satellites
The transportation of cargo to space is expensive. The high cost is partially attributable to the aggregation of multiple, costly individual operations that are needed to transport and deploy satellites and other cargo to orbit. The latter part of the orbital transportation operation, i.e., transporting the payload from low earth orbit to the desired final higher orbit, is typically accomplished by an upper, or final, stage. This stage is ignited and transports the payload to the final orbit. Sometimes this stage remains attached to the payload, satellite, or cargo; but it is usually discarded in orbit. Upper stages vary in their capability of independent actions from a passive, simple, small, solid rocket motor just providing additional propulsion capability, which goes in the direction it is pointed when ignited, to very capable, restartable, liquid rocket engines capable of multiple restarts and significant maneuvering using thruster(s) and related avionics. Some active upper stages are able to dispense multiple satellites.
Launch vehicles used to deploy satellites in a predetermined orbit are evolving from expendable, and partially expendable rockets, toward fully reusable launch vehicles (RLVs) capable of multiple reuse. The primary advantage of RLVs is the potential for significant cost savings. RLVs frequently utilize active satellite dispensers and upper stages. Satellite launch systems still include a device that couples the satellite to the launch vehicle; but in today""s world, this dispensing hardware takes on a more active role than the simple release of the satellite in response to a control signal. Recent reusable vehicle advances, technological improvements, and commercial market forces are moving the satellite industry toward smaller, more sophisticated commercial networks of communications satellites requiring multiple satellites in various orbital planes around earth.
The increased demand for communication satellite networks and higher orbits has given rise to active, more capable, customer-sensitive satellite dispensers that satisfy the new privately-financed communication network markets. The new commercial networks require innovative satellites of different size, weight, and transportation requirements. Existing satellite dispensers lack the flexibility and cost effectiveness of reusable vehicles. Moreover, existing satellite dispensers lack subsystem commonality, propellant compatibility, and/or the ability to adapt to the emerging reusable launch vehicles. Existing satellite dispensers fail to adequately take advantage of the reusable vehicles"" reusable shrouds and orbital satellite release techniques.
Previous dispensers stack multiple satellites vertically, and therefore typically employ discardable shrouds that can clutter the orbital environment with spent hardware, which can endanger other space operations. Shortly, international agreements are expected to limit the placement of satellites to those systems that minimize the debris impact on others.
U.S. Pat. No. 5,568,901 to Stiennon, entitled xe2x80x9cTwo Stage Launch Vehicle and Launch Trajectory Method,xe2x80x9d is purported to be a fully reusable launch vehicle, but fails to mention anything of a satellite dispenser.
The space shuttle is a partly-reusable vehicle and has several expendable satellite assist modules, or third stages, but at significant cost and requiring extensive hardware dispensers specific to the shuttle payload bay and, in some cases, requiring the changing of the axial orientation of the satellite by a significant amount or to exit the payload bay via a Frisbee(copyright)-throwing method.
U.S. Pat. No. 5,242,135 to Scott et al., entitled xe2x80x9cspace Transfer Vehicle and Integrated Guidance System,xe2x80x9d is a space transfer system capable of continuing the propulsive cycle of earlier stages, but lacks the full service structure system to handle the new generation of communications satellites. No provision for both forward and sideways satellite ejection appears to be available from this patent. No shroud reuse or any reuse of any hardware, except the space transfer vehicle, is implied. No provision in the hardware is evident for disposal at end of life.
U.S. Pat. No. 5,884,866 to Steinmeyer et al., entitled xe2x80x9cSatellite Dispenser,xe2x80x9d is a dispenser for the 1990s, but has no propulsion or other active subsystems. The post can accommodate the newer network communication satellites, but it appears the entire upper stage of the poorly defined launch vehicle must be taken to each individual orbit for satellite dispensing.
U.S. Pat. No. 5,337,980 to Homer et al., entitled xe2x80x9cSpacecraft-to-Launch-Vehicle Transition,xe2x80x9d is more a structural connection between a vehicle and a satellite, rather than a dispenser. The drawings seem to depict a rocket engine, but it appears to be a part of the satellite. The adapter and/or structural hardware appears to have no active dispensing function except a release capability.
U.S. Pat. No. 5,199,672 to King et al., entitled xe2x80x9cMethod and Apparatus for Deploying a Satellite,xe2x80x9d is a solid rocket version of a dispenser designed to place many small satellites into a specific orbital plane and focuses on the specific design to accommodate the Pegasus. The four separate pallets are fired into different orbital planes by waiting to fire the solid rocket motors at different times as the earth turns below.
U.S. Pat. No. 5,816,539 to Stotelmeyer et al., entitled xe2x80x9cIntegrated Storage and Transfer System and Method for Spacecraft Propulsion Systems,xe2x80x9d is an orbital assist module (OAM) built into the stack of an expendable launch vehicle (ELV). The orbital assist module propellant comprises hydrazine and is difficult to handle.
In contrast, the present invention uses propellants, preferably liquid propellants, used in a single, pressure-feed engine that preferably utilizes components having commonality with the reusable launch vehicle. This hardware commonality in engine, main propellants, pressurants, radiation-hardened avionics, and attitude control systems (ACS), including the propellant used in the ACS tanks, reduces the testing, procurement, ground handling, support systems, andxe2x80x94most importantlyxe2x80x94the cost. The propellants used also lend themselves to increased ground safety and cost-effective operations within the present invention.
Although the present invention will be described with reference to a preferred embodiment that is designed to be used with the K-1 reusable launch vehicle system, which includes a launch assist platform and an orbital vehicle (hereinafter, the K-1 orbital vehicle, or the like) currently under development by Kistler Aerospace Corporation, it will be appreciated by one of ordinary skill in the art that the invention can be readily adapted for use with other launch systems without departing from the spirit and scope of the disclosed invention.
A primary object of the active dispenser is to transfer the satellite to a higher orbit and position it in the proper orbital location in a cost-effective manner.
An advantage of the present invention is the cost-effective combination of a reusable launch vehicle subsystem, including efficient propulsion subsystems, pre-engineered common computer avionics, propellant, pressurant, and attitude control thruster hardware subsystems, and a dispenser for multiple satellites.
An advantage of the active dispenser on a reusable launch vehicle is the ability to integrate commonality with subsystems used on the launch vehicle and/or satellite hardware providing cost-effective common subsystems through commonality in design, procurement, testing, and propellant loading.
Another advantage of the invention is the ability to integrate common ground handling techniques, technical maintenance, financing, and ownership of the active dispenser, launch vehicle, and satellites.
Another advantage of the invention is an integrated commercial, satellite delivery operation that all works together in a cohesive manner to accomplish the ground processing, launch, transfer to the proper orbit, release of the satellite, and potential follow-on support.
Another advantage of the active dispenser is an integrated design, flexible enough to be capable of accommodating on a general active dispenser, a number of different satellites from numerous organizations with varying requirements, different weights, various final orbits, different ground processing requirements, and varying financial needs.
Another advantage of the invention is the increased energy efficiency in the use of liquid propellants, including the liquid storable propellants, the decreased cost in simplifying the ground handling by using the storable propellants, increased flexibility from the restartable orbital propulsion, and the increased reliability and simplified handling from the common, pre-tested hardware and propellant systems.
Another advantage of the invention is a single, pressure-fed, restartable, liquid bipropellant main engine located at the base of the active dispenser, which fires to propel the active dispenser into its proper orbit.
Another advantage of the active dispenser is a reusable, conical payload adapter at the base of the dispenser and a clampband that attaches the K-1 vehicle or other vehicles to the active dispenser.
Another advantage of the invention is the K-1 orbiter or other launch vehicle, which opens its payload module dome in orbit and deploys either vertically or horizontally everything above the clampband into space.
Another advantage of the invention includes the various satellites with different shapes that are able to be attached to the support mast using adaptable structural interfaces.
Another advantage of the invention is the small thrusters mounted to the active dispenser used for attitude control, a pallet for avionics hardware, and gas storage bottles for pressurization and attitude control.
Another advantage of the invention includes two similar tanks (one or more for fuel and one or more for oxidizer) mounted on either side of the support mast, which connects the engine to the propellant via feed lines.
Another advantage of the invention is the propulsion system design using hardware common to the K-1.
Another advantage of the invention is that the propellant tanks are pressurized by gas storage bottles filled with pressurant gas.
Another advantage of the invention is an active dispenser avionics system, which uses the radiation-hardened hardware for control as the K-1 orbital vehicle.
Another advantage of the invention is the avionics system, which uses a triplex computing architecture with three cross-strapped 1553 avionics databases and a hardware voter.
Another advantage of the invention is the electronics power, which is triply redundant, and the utility power, which is dual redundant.
Another advantage of the invention is the flight software, which is a modified version of the software used on the K-1 orbital vehicle.
Another advantage of the active dispenser, in a nominal mission mated with one or more customer satellites, is its being processed, handled, fueled, and mated to the K-1 payload module in the K-1 payload processing facility, using the same hardware, consumables, and staff already on hand for other similar hardware on the existing reusable launch vehicles.
Another advantage of the invention is that the orbital vehicle deploys the active dispenser and satellites after it reaches a nominal 200 km circular orbit at the desired inclination, depending on the mission.
Another advantage of the invention is achieved after adequate clearance between the active dispenser and orbital vehicle is achieved and the active dispenser performs a series of burns used to place the satellites into their desired final orbits, without further assistance form the launch vehicle.
The active dispenser places satellites into higher orbits than the host launch vehicle. This third stage is cost-effective because it combines the advantages of a reusable launch vehicle with the flexibility and common subsystems.
In a nominal mission, the active dispenser is mated with the customer""s satellite in an off-line vehicle processing operation, including propellant loading, and mated to the K-1 payload module in the K-1 payload processing facility. The launch vehicle deploys the active dispenser and satellites after it reaches a higher circular orbit at the desired orbital inclination. The active dispenser initiates a series of burns to place the satellites into their desired final orbits.
Other objects, advantages, and novel features, and further scope of applicability will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, FIGS. 1-5, and, in part, will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the inventions particularly pointed out in the appended claims.